This invention relates to an auger apparatus, and more particularly to sweep augers suitable for moving granular material across the floor of a circular storage bin toward the center of the bin.
Sweep augers have long been used to unload grain or other granular material from circular storage bins. In such apparatus, a radially disposed auger rotates about its own axis to drag the granular material to an unloading sump at the center of the bin. Simultaneously, the auger revolves around the central vertical axis of the bin to advance across the bin floor in a sweeping action. The auger shaft typically is rotated by power means connected to the radially inner end of the shaft. A drive wheel often is attached to the radially outer end of the auger shaft for rotation therewith to support the outer portion of the auger, as well as to assist in driving the auger in its sweeping motion. While such arrangements provide for ease of manufacturing, certain operating and other disadvantages are inherent in the equipment. Auger shafts typically rotate at several hundred revolutions per minute to achieve the desired unloading capacity. However, this results in a peripheral velocity of the support wheel which is far greater than the rate of advancement of the outer end of the auger and hence of the wheel. This results in excessive slippage of the wheel on the support floor. Hence, the drive wheel wears out quickly if its periphery is made of rubber or other relatively soft traction material, as is desirable to provide sufficient frictional engagement with the steel bin floor to accomplish the sweeping motion. On the other hand, if the drive wheel periphery were made of steel or other hard material, the wheel often would not provide adequate traction for satisfactorily advancing the auger into the granular material, and would wear the bin floor.
In the past, the aforesaid disadvantages have been overcome or minimized only with more complex apparatus and at considerably greater expense. In one such instance (see U.S. Pat. No. 3,127,032) a separate drive shaft extends coaxially through the auger shaft and drives a sprocket at a rotational speed independent of the speed of the rotating auger, the sprocket engaging a circular perforated track to provide a positive drive during the sweeping action. In other instances, auxiliary motors have been provided to drive sprockets or gears which similarly engage circular tracks to effect a positive drive for sweeping (see e.g., U.S. Pat. Nos. 3,356,235; 3,391,809; and 3,489,643). In yet another instance (see U.S. Pat. No. 4,063,654), a sweep auger shaft rotatably carries a floor engaging wheel which rides on a smooth portion of a circular track and, in addition, speed reduction gearing is driven from the auger shaft to operate an eccentrically mounted drive ratchet which engages a toothed portion of the track to effect a positive drive during the sweeping action. All of these constructions are unnecessarily cumbersome and expensive.
More recently (see U.S. Pat. No. 4,701,093) a speed reduction drive system having a sprocket mounted on a shaft to engage a sprocket chain secured to a drive wheel is coupled to the auger and drives the wheel at a reduced speed relative to the rotation of the auger. The speed reduction ratio is determined by the dimensions of the sprocket and sprocket chain which based on size limitations due to the construction of sweep augers, makes certain higher speed reduction ratios impracticable.
A higher speed reduction ratio between the rotational speed of the auger and that of the drive wheel is desired as slower rotational speed of the drive wheel extends the life of both the drive wheel and the floor since the surface areas of both the wheel and the floor will not wear down as fast. In addition, higher speed reduction ratio places less stress and bending on the end of the backboard and allows more time for grain to be transported away along the middle of the sweep auger. The need for a higher speed reduction ratio increases as storage bins get larger, for both of these reasons.
It is an object of this invention to provide improved drive arrangement for sweep augers.
A further object of this invention is to provide an economical sweep auger apparatus which avoids the problems of the aforementioned apparatus.
Another object of the invention is to provide an improved sweep auger apparatus which enables the auger shaft to be rotated about its longitudinal axis at a speed sufficient to achieve the desired bin unloading capacity and at the same time to drive a drive wheel on the apparatus at such sufficiently lesser speed than conventional devices that the wheel engages the bin floor with greatly reduced slippage as the auger revolves around the central vertical axis of the bin in unloading material from the bin.
A further object of the invention is to provide a sweep auger apparatus which may be effectively employed to unload granular material from a circular storage bin without requiring a special circular track or the like around the periphery of the bin floor to effect a positive drive for the sweeping action.
A still further object of this invention is to provide an economical sweep auger apparatus in which a single power source is employed both to rotate the auger about its longitudinal axis and to rotate the drive wheel which supports the radially outer end of the auger at a substantially lesser speed.
These and other objectives will become apparent to those skilled in the art based on the following disclosure.